I read this method of ebonizing wood in
a book by Tage Frid a long time ago. It works well on any wood that
water will penetrate into. Some woods, like rosewood and lignum
vitae do not respond well to this treatment because they don’t
absorb water very well.

Here are the two ingredients I use:

Rusty Vinegar

I use common household vinegar. I
add rusty nails, screws, and other rusty Iron as I find it.
The vinegar will slowly dissolve the rust into solution. At
the suggestion of someone on the oldtools list I once tried using
steel wool. Steel wool makes a horrible mess in the vinegar,
and I never tried it again. It does work, but it is nasty. I like
the dissolved rust much better.

The Tannic Acid I use was obtained from a chemical supply
house. As I recall 500 grams cost about $60. I repackaged and
sold a few 2 ounce packages to other Galoots to help defray some of
the cost.

The speed of the reaction of the rusty
iron solution in the tannic acid depends on the strength of the
solutions. If the tannic acid solution is quite strong, then
the blackening will take place almost immediately. I do not
measure the amount of the acid powder I dissolve in warm water.
I just add powder until I have a pretty dark mixture.

I also do not measure the vinegar and
iron. I just keep adding rusty iron to the vinegar until no
more will dissolve. That is known as a saturated solution. You
will know when the solution has enough rust in it because rust will
stay on the iron no matter how long you leave it in the vinegar.

Step 1 - Applying Tannic Acid

Flood the Tannic Acid solution onto the wood. Then
wait for it to dry. I have used a piece of walnut and a piece of
alder here for this demonstration. One dark wood and one light
colored wood.

Step 2 - Apply Rusty Iron/Vinegar solution

Here I have just applied the rusty iron/vinegar solution to the
wood. The reaction time is so fast that I couldn’t take a picture of
the application. I only applied the solutions to the top of
the wood.

The stuff on the sides is just excess that ran down.
The tannic acid solution is in the picture because I wanted you to
see the color of the solution when it is strong enough.

I find that the black color is enhanced by the application of a
thin coat of garnet shellac to the ebonized surface. The color
without the garnet shellac is a little too cold for me. It looks
better to me warmed up a little with the garnet shellac.

The black color goes into the wood about 1/32” deep, depending on
the hardness of the wood. You should raise the grain in the wood
before you apply the acid so that raised grain will be minimized
after the treatment. It is quite possible to sand through the color.

There are several other methods of ebonizing wood. I like this one
best.